This invention relates to a pump overload control for a water supply system; for on/off means of power supply; for shutting off the pump motor in the event that the current to the motor is at a damaging level; to provide protection for the pump motor and pump; to indicate overload, power on and pump run; with novel installation means.
The conventional electrically operated pump in a residential water supply system has motor branch-circuit, short-circuit and ground-fault protection provided by a circuit breaker in the electrical entrance panel of the power source. The circuit breaker is generally rated at 300 percent of full-load current to carry the starting current of the motor without nuisance tripping. The motor is protected against overload by an automatic resetting thermal protector within the motor to prevent dangerous overheating of the motor due to overload and failure to start. This overload protector is generally rated at 115 to 140 percent of full load amps. When the motor load exceeds this predetermined amperage level, and continues to run, the overload protector will heat up, open the motor circuit and stop the motor to stop the heat damage. While the motor is off, the heat dissipates and the motor cools. When the overload protector cools, it automatically resets and restarts the motor, further subjecting it to dangerous overheating.
This automatic reset type overload system has resulted in undue damage to the pump motors and often to pumps in many situations including waterlogged tank, abrasives in water supply, pump running dry, improper electrical power source, and damaged or undersized wiring to name a few. In these situations the motor runs at overload amperages until the overload protector heats up and stops the motor, but once it cools it restarts the motor again. If the overload amperage condition still exists and is not high enough to trip the short-circuit/ground-fault circuit breaker in the entrance panel, the motor is subject to this overload heat up and shut off, cool down and turn on cycle again, and subsequently, over and over again. Hence if this damaging heating/cooling automatic cycle continues unnoticed and the motor continues to draw excessive amperage, up to 300 percent of its full load amps without tripping the circuit breaker, the overload problem becomes severe enough to cause damage or failure to the motor or motor circuit, and consequentially the pump.
Simple prior art controls used to stop this damaging heating/cooling cycle have included a dual element fuse in an enclosure. A dual element fuse can be sized close to the full load current of the motor and provides overload protection that supplements the built-in overload protection of the motor. Now when the motor is subject to overload the fuse blows and stops the motor permanently, not allowing the automatic reset overload protector in the motor to go through its heating/cooling cycle which can damage the pump.
Prior art controls above have been deficient in that: the fuse is not resettable, once it blows it must be replaced; replacement fuses are added expense to purchase and find; the enclosure requires wall mounting and if the pressure switch is mounted seperately on the piping this requires multiple electrical connections, excess wiring and added time and space for installation; if the pressure switch is mounted with the enclosure, special mounting, reinforcement or bracing is required to connect and support the pressure switch to the enclosure; when the pressure switch is mounted with the enclosure, prewiring is limited to load side of fuse to line side of pressure switch, this still leaves multiple electrical connections for installation; when the pressure switch is mounted with the enclosure, special piping to the pressure switch is required for this remote installation. Lastly, these prior art controls do not indicate to the owner what their water pumping system is doing. They do not indicate whether the electrical power source is on; whether the power source is running through the pressure switch to indicate pump run; and when using cartridge type fuses they do not indicate when they open under an overload condition.